I looked at the nautical charts for Black sea[0]. It looks like the area near Odessa is quite shallow (less than 100m (~300ft) deep). I'll hazard that it was a total loss from a get go, but they towed it just far enough to be able to let it sink to deeper waters (like 1000+ m deep (~ 3000ft)).

[0] https://www.oceangrafix.com/chart/zoom?chart=55001